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1227747 $42 VE1 + VE2 Fuel Tables

The screen shots below show how to add the '7747 VE1 + VE2 tables.

It's my understanding that once the '7747 ECM goes above 3200 RPM's, the ECM will use the last known VE value from the 3200 RPM table. Typically, the 3200 RPM VE values are at or above 90's ( VE1 + VE2). It's very likely an engine operated by a '7747 at or above 3200 RPM's will already be above 80 Kpa.

With the correct BPW the ideal VE1 + VE2 table will have low numbers in the low 40's and the high numbers will be no higher than the mid 90's.

I must say, configuring the VE tables using daves method of VE1+VE2 has given me better results than anything else I've tried as far as messing with the fuel tables in the 747.

I added my VE tables together using daves method, then slewed the whole table down a few points so that no VEs were over 100, or close to for that matter. I've done several logs and adjusted the fuel table down and now, my highest is like 88 and lowest is like 22. This is after a few BLM adjustments using daves VE calc spreadsheet

I haven't checked BLM since doing the last adjustment but I expect them to be +/-3 in most areas..

dave, you said ideally the lowest VE should be low 40s and highest mid 90s. Really anywhere is OK though as long as you're not maxed out to either extreme 0 or 100 right? I used yet another handy tool of yours, the BPW spreadsheet you created, and came up with my BPW, dropped it into the tune, combined VEs, slewed main VE down a bit and proceeded to collect BLMs. After a few BLM logging sessions my lowest VE is now ~22 and highest VE ~88.

No that was not me nor is it correct, VE Volumetric Efficiency has to be correct weather low or high. Just can not exceed 95 in highest cell and lower is better.

Originally Posted by CDeeZ

I haven't checked BLM since doing the last adjustment but I expect them to be +/-3 in most areas..

Can't get much better then that, even if you did it would change with weather.

The reason Dave W BLM Spreadsheet works so well with this method is it's adjusting 100% of the value, what it is designed to do. If you still had VE2 then... lets say VE2 had 39% rounded to 40% for simplicity. Then you applied the spreadsheet calculations to VE1 which is the other 60%, so you have adjusted 60% of total VE not 100%.

Since Dave brought this up and seems to be of intrest I'll give some calibration theory taking from some of the best calibrators/tuners.

First adding VE2 to VE1 fueling table is usually easy and only one number, (Refer to Dave W first post) for instance ADSU is 39.06 for the entire VE1 table, use the Offset +/- tool in TunerPro and add it in, zero out VE2 and save bin with new name protecting your starting bin. This is what you end up with.

Stock with VE1 and VE2 added together.

1227747 $42 does not have a big resolution of table compared to later masks with say double the amount of cells. Tuning basics says to start with a smooth table, open your wireframe veiw and do some manual smoothing to make the table look more consise, then use the smooth tool to finish it off one cell at a time or row by row, setting it to .10 is a huge smooth and .90 is a small adjustment, I use .5 so it ends up something like this below.

So where do you start? Well if you look at the table, not wire frame, basically leave all four corners alone. Max number in bottom right should be no higher then 95 max, lower is better if you have big enough injectors and fuel pressure to support engine HP.

After smooth.

Reason for this is the way the ECM/PCM get's it's VE number for a given cell, say your using data tracing or the engien is running in this cell.

Well the ECM/PCM does not use that cell alone! It is a calculation of that cell plus four surrounding cells.

With that you can understand how and why it's easier and more accurate let alone easier for the ECM, in this case a slow ECM to make adjustments to fuel as needed.

In the end of tuning and making adjustments via BLM readings and a spreadsheet the final tune would look something like this.

Wouldn't you want to smooth the final table over a little bit after making BLM adjustments, since the ECM uses surrounding cells in making VE calculations

VE Tuning has some very individual opinions, like some add VE1 + VE2 some don't. Some will smooth, while again others don't. Every engine is different, some work fine with smoothing, while other engine work best with spikes, valleys, and peaks in the VE Table. The data is the data, which is the final judge if adding VE1 + VE2 or smoothing is working for the engine being tuned. I use Excel to tune with, other have excellent results tuning without Excel.

Wouldn't you want to smooth the final table over a little bit after making BLM adjustments, since the ECM uses surrounding cells in making VE calculations

In theory you could smooth the last table in the above post, record data and adjust, smooth, data, adjust, rinse and repeat... but the last table shown is well within boundaries of a good tune for that engine.

Reading several tuning books including all of Greg Banish books, when a tune comes together and data or wide band is inline all engines will show a torque hump. I actually found this before studying and tried to tune it out for a final tune without success, then noticed a pattern as I tuned more vehicles. This may not be the case in a race engine that has nothing but WOT high RPM HP. Hard to see it in the low resolution 7747 table/wire frame view but if you look you will see a hump where max engine torque is developing low RPM mid MAP, this is a demand for more fuel. As engine RPM increase demand goes down in wire frame graph and become smoother, but numbers are actually higher due to graph.

See the torque hump at 65 to 75 MAP, 1200 to 2000 RPM? This is typical of a close to stock TBI engine. Something like an LT1 would be bigger and higher do to engine demands and also look bigger do to table resolution having twice as many cells... more IIRC...

You also have to realize there are many cells in the picture or wireframe graph or your VE table that the engine will never hit! Take for instance 400 RPM 100 MAP and that area. Or 3200 RPM 20 MAP? Look at your BLM logs! Can you fill in all cells?

Great information here gentlemen. This kind of stuff gets me thinking, which is why I joined this site :)

You know, I was thinking that it would be best to adjust all (or at least most) cells in the VE table, even though some you can't collect data on like Marks' example of 400 RPM and 100 MAP; or 3200RPM and 20MAP. I was thinking it would be best to adjust all cells whether you got data in those cells or not, that way you could avoid spikes and dips in the VE table, but now ya'll got me thinking that maybe this is just not necessary or ideal to do the VEs that way. I guess really the data is the final judge, as dave stated.